24 AQUATIC PHYCOMYCETES 



twigs of ash or birch, or apples, pears, or the like in a galvanized per- 

 forated metal container or closed test-tube basket, or one of wire 

 screening, and submerge it — well concealed and anchored — in a fav- 

 orable locality. After a month or more the material can be brought 

 back to the laboratory in a jar or in very wet paper, the surrounding 

 slime (which should be examined for pythiaceous fungi) washed off, 

 and samples made of various pustules and filamentous fungi. This 

 material should be worked intensively immediately after collection, 

 since the changing environmental conditions generally induce quick 

 zoospore production. Samples of minute pustules as well as of the 

 larger ones should be made, for the former are not always merely im- 

 mature plants of larger species but often belong to totally different 

 ones. Submerged fruits and twigs are a prolific source of other fungi 

 as well as of Blastocladia. For example, Macrochytrium, a chytrid, 

 Gonapodya and Monoblepharis, members of the Monoblepharidales, 

 and Apodachlya, Rhipidium, Sapromyces, Araiospora, and Mindeniella 

 of the Leptomitales, and Phytophthora of the Peronosporales have all 

 been reported from these substrata. 



The other habitat in which members of the Blastocladiales occur 

 is soil. Although species of Allomyces, the commonest terricolous 

 form, are occasionally found in standing water, they have been iso- 

 lated most often from either permanently or periodically wet soil. 

 In the preparation of water cultures with soil samples battery jars 

 full of water are sterilized. After the water has cooled, the soil (about 

 one or two tablespoonfuls are sufficient) is dumped in and the culture 

 baited with an appropriate substratum. Boiled split hempseed or ca- 

 davers of fruit flies are the baits most frequently used. In the isolation 

 of Allomyces it appears almost essential that a large volume of water 

 cover the sunken bait. 



The highly specialized parasites of mosquito larvae belonging to the 

 Coelomomycetaceae are, of course, to be looked for wherever the hosts 

 occur. Temporary pools support different forms from the ones in per- 

 manent bodies of water. The Catenariaceae are essentially similar to 

 the aquatic chytrids in their habitat (see p. 650). 



Like the closely related Blastocladiales, the members of the Mono- 

 blepharidales have been collected from standing water and from soil. 



